EXPLAIN EXTENDED Output Format in mysql

by satheeshkumar 2012-09-20 08:50:17

EXPLAIN EXTENDED Output Format in mysql,

The following list describes special markers that can appear in EXTENDED output displayed by SHOW WARNINGS:

->(expr)
The expression (such as a scalar subquery) is executed once and the resulting value is saved in memory for later use.

->(query fragment)
The subquery predicate is converted to an EXISTS predicate and the subquery is transformed so that it can be used together with the EXISTS predicate.

->(query fragment)
This is an internal optimizer object with no user significance.

->(query fragement)
The query fragment is processed using an index lookup to find qualifying rows.

->(expr)
A test to verify that the expression does not evaluate to NULL.

->(query fragement)
The query fragment is processed using a primary key lookup to find qualifying rows.

->(expr)
This is an internal optimizer object with no user significance.

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